28 August 1998

Green spin-offs found in GMfen beet trial

By Andrew Blake

NEW evidence of positive environmental spin-offs from a genetically modified (GM) crop is emerging in Cambs.

The GM technique making sugar beet herbicide-tolerant can slash weed control bills. But it can also encourage wildlife and may even allow growers to lure pests away from the crop.

So say Brooms Barn researchers running a trial on a weedy fenland site near Littleport, who stress that GM crop value and acceptability must be assessed case by case.

Roundup Ready GM beet, tolerant to glyphosate, gives growers plagued with weed beet a chance to make a fresh start, says weed specialist Mike May. Cheaper and better volunteer potato control to reduce nematode (PCN) infestations is another potential advantage, says entomologist Alan Dewar.

Main aim of the Monsanto-funded work is to examine the effects of leaving a GM crop unsprayed longer than normally practised with conventional varieties.

Herbicide cost for the conventional five-spray programme required to keep on top of weeds in the replicated small plots trials, to be taken to yield is £284/ha (£115/acre). Dense weed in the untreated crop means it will be unharvestable, notes Dr Dewar.

But normal herbicide practice, if successful, leaves crops barren and unattractive for wildlife, he notes. Two of three alternative dual spray glyphosate programmes, each costing £60/ha (£24/acre), have allowed far more insects and their respective predators to survive among the weeds. "We didnt expect them to be so prolific."

The key observation however is that crop establishment and probably output need not be compromised, though he admits there were few potentially virus-bearing beet aphids in the trial, most being of another species.

The finding opens up the possibility of sowing specific weeds or crops with the beet as alternative pest hosts, he suggests.

"Birds, particularly seed-eaters, could also be encouraged into the crop," he speculates. At another site he reports noticeably less bird damage to beet seedlings where weeds were present.

Proper precautions though, including hand-roguing bolters, will be needed to make sure herbicide tolerance does not cross into conventional weed beet, he warns. One way to reduce the risk would be to sow slightly later than normal, says Monsantos trials officer Cathy Cooper. "With the yield advantage we get you could afford to drill 14 days later to lower the chance of bolters."

Herbicide-tolerant GMbeet could offer environmental benefits, as well as better beet returns, say Alan Dewar (left) and Mike May.